A quick fed-batch saccharification strategy of wheat straw at high solid loadings improving lignocellulosic ethanol productivity

A quick fed-batch saccharification (QFBs) strategy of pretreated wheat straw at high solid loadings (HSL) was developed to achieve high sugar concentrations and increase lignocellulosic ethanol productivities in the fermentation stage. Pretreatment time, number of feedings, and the time between them were evaluated using a Box-Behnken design. A surface response model was employed to maximize sugars released at 20% (w/w) HSL. Total sugar concentrations after 60 h with 20% (w/w), 25% (w/w), and 30% (w/w) HSL were 128.5 g/l, 142.4 g/l, and 163.5 g/l, respectively. These were 14.6–42% higher than their batch saccharification counterparts. The QFBs was implemented as part of sequential (SHF) and simultaneous saccharification-fermentation (SSF) strategies as well as the presaccharification stage of a semi-simultaneous saccharification-fermentation (SSSF) strategy. In the latter strategy, the highest ethanol concentration achieved was 31.7 g/l. The ethanol volumetric productivity was 2.2- and 3-fold their SHF and SSF counterparts.